Hydrodesulfurization Catalysts Research Articles

A novel and facile strategy for the preparation of highly reactive NiMo/γ-Al2O3 hydrodesulfurization catalyst

Traditionally, the commercial Ni(Co)Mo(W)/Al2O3 hydrodesulfurization (HDS) catalysts were prepared with corresponding oxidation precursors and then sulfured with CS2 or H2S, which is complex and time-consuming. Herein, a novel “O-S exchanging” strategy was proposed to directly synthesize a series of highly efficient Ni-MoS2/Al2O3 HDS catalysts with various Mo loading using MoS42− solution as a novel active precursor, and their catalytic performances were evaluated for 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS. The experimental results showed that under the same reaction conditions, the catalyst with 15 wt% MoO3 (S-CAT-15) exhibited a HDS rate up to 99.8 % for 240 h, which was not only nearly two times higher than that of O-CAT-15 counterpart prepared by the conventional oxidation precursor with the same metal loading, but also even 1.6 times higher than that of O-CAT-20 with a higher metal loading, demonstrating its excellent HDS performance and outstanding stability. The deep characterization analyses unveiled that the superior HDS performance of S-CAT-15 was attributed to this novel strategy, which not only notably improved the sulfidation of Mo species, but also considerably promoted the decoration of Ni atoms onto the edges of MoS2 slabs forming more reactive Type-II Ni-Mo-S sites, thereby remarkably enhancing the HDS performances of S-CAT catalysts. This work may offer a novel protocol to guide the fabrication of more efficient industrial hydrogenation catalysts in the future.

Enhancing Co, Mo and Al leaching from spent HDS catalysts during scale-up process based on fluid dynamic and leaching mechanism

Large amounts of Mo, Co and Al are contained in spent hydrodesulfurization (HDS) catalysts, and recovering these valuable metals from spent catalysts achieves sustainable utilization of resources and promotes environmental protection. However, the leaching efficiency of valuable metal often experiences a sharp decline during scale-up. In this study, leaching experiments and fluid dynamics were used to jointly investigate the major factors and regulation mechanisms affecting leaching efficiency during the scale-up process. Optimization of flow field conditions is guided by Computational Fluid Dynamics (CFD) simulation. including different paddle types, agitation speed and particle size. After controlling flow field assisted with CFD simulation, about 20% of the sulfuric acid solution was saved and 99.7% of Mo, 98.2% of Co and 83.7% of Al were successfully recovered. Additionally, the leaching mechanisms of these metals in H2SO4 were systematically studied. The findings indicated that the leaching kinetics of Co, Mo and Al are governed by diffusion-controlled model, consistent with the shrinking core model. Correlation coefficients and activation energy analyses further demonstrated that the leaching process is diffusion-controlled, highlighting the importance of flow field mixing in scaling up the acid-mediated recovery of Mo, Co and Al from spent HDS catalysts. The fluid dynamic and leaching mechanism study provides valuable insights for large-scale recovery of valuable metals.

Engineering the accessibility of active sites in mixed 1 T-2H MoS2 nanoflowers via NaClO etching for deep hydrodesulfurization of dibenzothiophene

A NaClO etching strategy was adopted to engineer the active structure of mixed 1T-2H MoS2 nanoflowers and prepare efficient hydrodesulfurization (HDS) catalysts. In the original MoS2-P catalyst, the 2H-MoS2 phase was exposed after MoS2 slabs were etched using NaClO. Sodium ion insertion with high concentrations increased the interlayer spacing of MoS2 slabs and increased the transformation of 2H-MoS2 to 1T-MoS2 phases. With increase in the concentration of NaClO solution, the proportions of 1T-MoS2 in the MoS2-N-x catalysts initially increased and then decreased. They then reached a maximum when the NaClO concentration was 1.0 mol/L. Owing to the thermodynamic instability of 1T-MoS2, the proportions of 1T-MoS2 in the sulfided MoS2-P and MoS2-N-x catalysts were less than those of the corresponding unsulfided catalysts. However, among sulfided MoS2-P and MoS2-N-x catalysts, the sulfided MoS2-N-1.0 catalyst demonstrated the highest proportion of the 1T-MoS2 phase, the best dispersion of the MoS2 slabs, and the most coordinatively unsaturated sites, thus providing itself with the optimal HDS performance for removing dibenzothiophene.

Extraction of molybdenum, cobalt, and nickel from acidic leach solution of molybdenum leach residue of spent hydrodesulfurization catalyst

ABSTRACT After the extraction of molybdenum from the spent HDS catalyst, a residue containing aluminum, nickel, cobalt, and a small amount of molybdenum was obtained. The simultaneous recovery of nickel, cobalt, aluminum, and residual molybdenum from molybdenum leach residue can be achieved through hydrochloric acid leaching. In the work presented herein, the extraction of molybdenum, cobalt, and nickel from the acidic leach solution of molybdenum leach residue was investigated. Trioctyl tertiary amine can selectively extract cobalt and molybdenum from the acidic leach solution, the extraction of both cobalt and molybdenum reached more than 99% after two-stage countercurrent extraction. The combination of pure water and 25% ammonia water can be utilised for the separation and extraction of cobalt and molybdenum from the loaded cobalt-molybdenum organic phase. After the extraction of cobalt and molybdenum, a synergistic extraction system comprising decyl 4-picolinate and dinonylnaphthalene sulfonic acid can be employed for nickel extraction, achieving a nickel extraction exceeding 99.70% while maintaining aluminum extraction at only 0.32% after undergoing four-stage countercurrent extraction. The nickel stripping efficiency can reach 99.50% after four-stage countercurrent stripping, using a stripping agent of 2 mol/L H2SO4.

A Comprehensive Comparison Analysis between Ammonium-Based and Phosphonium-Based Bifunctional Ionic Liquids for Metal Extraction and Separation Processes.

A phosphonium-based bifunctional ionic liquid (IL) Cyp-IL was synthesized to recover molybdenum and vanadium from industrial waste resources, such as the spent hydrodesulfurization catalysts. In comparison with the reported versatile Aliquat 336-based ionic liquid, the developed ionic liquid Cyp-IL was investigated for its potential application recovery of vanadium and molybdenum from industrial wastes. To assess the efficiency of the comparative extraction process, a comprehensive comparison analysis was conducted between the ammonium-based bifunctional ionic liquid Aliquat 336 and the developed phosphonium-based bifunctional ionic liquid Cyp-IL. Vanadium and molybdenum in the ionic liquid-loaded phases were selectively precipitated using NH4Cl and BaCl2 solutions in a basic medium. Compared to Aliquat 336-based Ali-IL, Cyp-IL exhibited superior performance in the extraction and separation processes of molybdenum and vanadium such as a recovery rate of Mo 91% and V 82.5% vs Mo 85% and V 72% by the ammonium-based bifunctional ionic liquid Ali-IL. The recovered components, such as molybdenum and vanadium, were characterized by energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). This method capacitates the sustainable recovery of pure vanadium and molybdenum compounds while minimizing the environmental impact.

Bimodal mesoporous AlMCM-41 supported NiMo catalysts for efficient hydrodesulfurization of 4,6-dimethyldibenzothiophene

In this research, a bimodal mesoporous AlMCM-41 (B-AM41) material was prepared and applied to support NiMo catalysts for the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene. Additionally, catalysts supported on smaller and larger single-pore AlMCM-41 (S-AM41 and L-AM41) were also prepared as reference catalysts. Detailed characterizations show that the proportion, stacking degree, and length of the MoS2 active phase on the different catalysts are distinct. As a result, HDS evaluation indicates that the NiMo/B-AM41 catalyst exhibited better catalytic activity with a reaction rate constant of 10.4 × 10−8 mol g−1 s−1 and a turnover frequency of 7.0 × 10−4 s−1, significantly surpassing the S-AM41 and L-AM41 supported catalysts. The superior activity of the NiMo/B-AM41 catalyst can be attributed to a high sulfidation degree that provides sufficient highly dispersed type Ⅱ MoS2 phases with minimal stacking and moderate slab length. Moreover, the bimodal mesoporous structure promotes the diffusion of 4,6-DMDBT and benefits its contact with active sites.

Speciation of the Oxide Phase of Molybdenum‐Based HDS Catalysts Enhanced with Organic Additives Using an EXAFS/Raman Coupling Methodology

AbstractThe ability to gain access to the speciation of hydrodesulfurization (HDS) catalysts used for removing sulfur and nitrogen from transportation fuels is becoming a key feature in the understanding and improvement of their catalytic activity with the aim of reducing greenhouse gas emissions of fossil fuels. A novel coupling methodology between Raman spectroscopy and X‐ray absorption spectroscopy (XAS) was developed, which allows for precise qualitative and quantitative analysis of the oxide phase of Mo‐based catalysts. This enabled the detailed study of various impregnation parameters and the characterization of HDS catalysts before sulfidation. To illustrate this methodology, the effects of two additives (triethylene glycol and citric acid) were studied. The results demonstrated that organic additives exert a profound influence on the speciation of oxide precursors of molybdenum‐based catalysts. The presence of these additives enhances the dispersion of Keggin or Dawson heteropolyanions (HPAs) on the support by maintaining a high phosphorus‐to‐molybdenum ratio in solution. This is achieved by two strategies: triethylene glycol (TEG) exhibits a pronounced affinity for alumina hydroxyls, while citric acid compensates for phosphate adsorption through the formation of a stable Mo‐citrate complex.

Unveiling the degradation mechanism of cathodic MoS2/C electrocatalysts for PEMWE applications

Molybdenum dichalcogenides (MoS2) are promising non-noble alternatives to replace platinum (Pt) for Hydrogen Evolution Reaction (HER) electrocatalysis in Proton Exchange Membrane Water Electrolyzers (PEMWE). The knowledge acquired on this class of catalyst for hydrodesulfurization (HDS) reactions has enabled significant advances in designing active MoS2 for HER. However, the stability of MoS2 in the dynamic operating conditions of a PEMWE coupled to renewable energy sources is often overlooked in the literature and is the focus of the present work. Herein, using nano slabs of 2H MoS2 supported on high surface area carbon, we dynamically monitored Mo dissolution trends both under HER conditions and at more anodic potentials to mimic start-ups and shut-downs of a PEMWE device. We report minimal Mo dissolution under HER conditions but it continuously increased with higher electrode potentials. In particular, Mo dissolution peaked during the irreversible oxidation from Mo(IV) to Mo(VI) starting at E = 0.7 VRHE which in turn fully annihilates HER activity. Since no change in Mo and S surface composition was observed, the decline in HER activity was attributed to the continuous exfoliation of the 2D MoS2 stacked layers induced by oxidation/dissolution of Mo. Additionally, our findings indicate that Mo cations can redeposit onto the cathode catalytic layer, forming a Mo blue film primarily composed of Mo(VI) species. This redeposition hampers HER performance by blocking catalytic sites and diminishing the catalyst's overall efficiency. These insights demonstrate the need to avoid excursions above E = 0.6 VRHE for the safe use of MoS2 cathode catalyst in PEMWE.

Hydrodesulfurization and isomerization performance of model FCC naphtha over sulfided Co(Ni)–Mo/Y catalysts

The process of deep hydrodesulfurization (HDS) in gasoline typically results in the saturation of olefins, leading to significant reductions in octane number. In this work, Y-supported Co(Ni)–Mo catalysts that with different Ni–Co content were prepared by the incipient wetness impregnation method, the structure and properties were characterized and analyzed using HRTEM, XPS, H2-TPR, and NH3-TPD. The isomerization of 1-hexene and 1-octene as well as the HDS of thiophene were studied by using model FCC naphtha. The incorporation of Ni was found to enhance the number of MoS2 stacking layers, thereby improving the degree of sulfurization in Mo and subsequently increasing the desulfurization rate, with a maximum achieved desulfurization rate of 94.7%. When employing a Ni/Co ratio of 3:2, optimal synergy between Ni and Co is achieved, resulting in a greater presence of multi-layer stacked II-Co(Ni)MoS active phases. Additionally, appropriate Brønsted acidity levels are maintained to facilitate efficient olefin isomerization while preserving high HDS activity. As a result, the current isomerization yield stands at 58.2%(mass). These understandings shed light on the development of highly HDS and olefin isomerization catalysts.

Insights into the Effect of a Microwave Field on the Properties of Modified γ-Alumina: A DFT Study

γ-Alumina is often used as a support for hydrodesulfurization catalysts due to its excellent performance. During the catalytic reaction, the strong surface acidity of γ-alumina can induce a strong interaction between the active phase and the support. The reaction activity of the catalyst can be affected by changing the present mode of the active phase on the surface of the support. The (110) crystal plane, acting as the strongest acidity plane of γ-alumina, was selected for modification. The supports modified with boron and phosphorus were successfully constructed, and the acid strengths were quantified by simulating the adsorption of the relevant probe molecules: pyridine in correlation with surface electronic properties via density functional theory. The surface adsorption energy calculation shows that the boron-modified surface is able to moderately reduce the adsorption capacity of alumina, while that of the surface modified by phosphorus is found to be enhanced over the sites of a tetrahedral coordination structure; however, at the other unsaturated Al sites, this is obviously reduced. The results of introducing electric fields imply that applying horizontal electric fields changes the surface acidity of alumina under the premise of a stable structure. With the enhancement of the horizontal electric fields, the adsorption capacity of tetra-coordination sites on the original surface gradually decreases, while those of the others gradually increases. However, for the boron-modified surface, introducing horizontal electric fields can reduce the adsorption capacity of all sites. Hence, microwave-electric-field-assisted modification of B further reduces the surface acidity of alumina, making it beneficial for deep hydrodesulfurization reactions.

Recovery of aluminum, vanadium, and nickel from waste desulfurization catalyst residue by roasting and water leaching

The improper disposal of hydrodesulfurization (HDS) catalysts poses significant environmental risks due to the presence of toxic materials and metals. This study investigates a method for recovering valuable resources, specifically aluminum, vanadium, and nickel, from industrial waste HDS catalyst residue. The process involves roasting the HDS residue at 300°C for 120 min with a 1:1 solid-to-liquid (S/L) ratio of residue to sodium hydroxide (NaOH). Subsequent water leaching resulted in the recovery of approximately 99% of Al(III) and V(V). The leaching kinetics of Al(III) and V(V) were found to follow the Shrinking-Core model, described by the equations X = kc.t and 1 − (1 − X)1/2 = kc.t, with activation energies (Ea) of 7.39 kJ/mol and 4.61 kJ/mol, respectively. The leach liquor containing Al(III) V(V) was treated with concentrated hydrochloric acid (HCl) at pH 9.5 to precipitate aluminum salt, while vanadium was extracted using ammonium chloride (NH4Cl) by adjusting the pH to 7.1 at 50°C for 30 min. The residual material was leached with 5% (v/v) sulfuric acid (H2SO4) in the presence of 15% (v/v) hydrogen peroxide (H2O2) to achieve maximum nickel dissolution, resulting in the recovery of 99% of aluminum as Al(OH)3 with 99.8% purity and 99% of nickel as NiSO4.6H2O.

Modulating the Reaction Pathway of Ni2P/Al2O3 by Introducing Different Noble Metals for Hydrodesulfurization of Diesel.

Regulating the reaction pathway of a hydrodesulfurization (HDS) catalyst to achieve ultradeep desulfurization of diesel is a low-energy-consumption yet effective strategy but remains a tricky challenge. Herein, we present a Ni2P/Al2O3 catalyst with mesoporous properties synthesized by a facile hydrothermal-temperature-programmed reduction and normal impregnation (TPRI) method, and then different precious metals with similar loadings were introduced to prepare M-Ni2P/Al2O3 (M = Pt, Pd) catalysts through incipient wetness impregnation. Their structures were analyzed by a series of characterization methods, and their catalytic performances were examined for 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS. The correlation characterization results revealed that the kind of precious metals significantly affected the surface acidity and then the metal-support interaction (MSI) between Ni2P and Al2O3. Among them, the Pt-Ni2P/Al2O3 catalyst exhibits superior HDS activity with 88.5% 4,6-DMDBT conversion to Pd-Ni2P/Al2O3 (76.3%) and pristine Ni2P/Al2O3 (58.6%) catalysts under reaction conditions of 3.4 MPa, 340 °C, and LHSV = 4.8 h-1. This should be due to the introduction of Pt, which significantly facilitates the dissociation rate of H2 and the subsequent generation of more active hydrogen species than Pd, thereby promoting the formation of Brønsted acid sites, remarkably facilitating the isomerization (ISO) pathway, and markedly enhancing the 4,6-DMDBT HDS conversion of Pt-Ni2P/Al2O3. This work provides an efficient protocol to tame the reaction pathway and thereafter the catalytic performance of the HDS catalyst in the future.

Synthesis, characterization, and performance evaluation of unsupported tetrametallic CoMoMnAl and CoMoZnAl catalysts for selective hydrodesulfurization (HDS)

New formulations of unsupported tetrametallic catalysts derived from layered double hydroxides (LDH) compounds were synthesized by a constant pH coprecipitation method, characterized, and evaluated in the selective hydrodesulfurization (HDS) of thiophene in the presence of cyclohexene. The layered double hydroxides were prepared using terephthalate (C8H8O2)2- as the interlayer anion with nominal aluminum molar fraction of 0.5, and nominal cobalt to MII (M = Zn or Mn) ratios of 0.2, 0.4 and 0.6. Molybdenum introduction in the LDH precursor was accomplished by an ion exchange process using the heptamolybdate anion. The calcined Mn samples showed a higher surface area than those obtained from Zn. The sulfidation was carried out in situ with a heating ramp up to 673 K and the catalysts were evaluated in a tubular flow reactor. The catalytic evaluation of Zn and Mn-based materials for simultaneous thiophene HDS and cyclohexene hydrogenation (HYD) was conducted at 573 K and 20 bar. The results show that the Zn-based unsupported catalysts synthesized here exhibited higher selectivity for the HDS reaction than an industrial one.

Weak interaction induced selective separation of V/Mo/Co from spent hydrodesulfurization catalyst leaching solution: Mechanism and strategy

Spent hydrodesulfurization catalysts contain more than 10 ∼ 25 wt% V, Mo and Co, which are not only hazardous materials, but also can be considered as valuable secondary resources. The complete separation of these complex critical metals by solvent extraction still needs to be improved. Here, a selective extraction route for the separation of V/Mo/Co is proposed based on the weak interaction differences between extractants and metal, which is realized by theoretical calculation and experimental verification. This process does not require pretreatment of N1923 and Cyanex272 (C272), thus reduced the consume of acid and base as well as generation of waste water. With the preliminary results of V/Mo, Co/Mo, and V/Co separation, the weak interaction between extractants and metal molecules was revealed by quantum chemical calculations quantitatively. The molecular charge distribution, surface electrostatic potential distribution (ESP) and the average local ionization energy (ALIE) shows the priority reactivity of the metal molecules as: H6V10O28 > H2Mo4O13 > H4V4O12 > H3VO4 > H2MoO4. The independent gradient model based on Hirshfeld partition (IGMH) show differences in the weak interaction forces as: N1923-V>C272-Mo > C272-V>N1923-Mo > C272-Co. The selective separation process of V/Mo/Co was designed with the guide of above results. The combined recovery of the three metals V, Mo and Co amounted to 83.88 %, 87.08 %, and 99.01 %, respectively. The whole route reduces 3.92 t sulfuric acid and 7.83 t sodium hydroxide per solid, and reduces 1.99 t carbon emissions compared to the conventional route.

Efficient and selective recovery of Mo and V from spent hydrodesulfurization catalysts via oxidation roasting followed by Na2CO3 and NaOH leaching

Spent hydrodesulfurization (HDS) catalysts containing large amounts of valuable metals, such as Mo and V, are hazardous solid wastes but also valuable secondary resources. However, the current recovery process suffers from the difficulty of balancing the leaching efficiency of Mo and V and their selectivity over Al. This work focused on the effect of phase transformation during roasting operation on the leaching behavior Mo, V, and Al and adopted an oxidation roasting followed by mixed alkali of Na2CO3 and NaOH leaching process to recover Mo and V from spent HDS catalysts. The results indicated that the phase transformation of Mo, V, and Al species during oxidation roasting process played a crucial role in achieving efficient leaching of Mo and V, as well as reducing leaching efficiency of Al. This transformation involved the change in Mo and V species changed from low valent compounds to high valent oxides, and Al2O3 from γ-phase to θ- and α-phases. In addition, efficient and selective leaching of 99.3% Mo and 97.8% V was realized, with only 0.03% Al being dissolved, by roasting the spent catalysts at 700 °C for 2 h and then leaching with a mixed solution of 1.2 mol/L Na2CO3 and 1.6 mol/L NaOH. The efficient and selective leaching of Mo and V can significantly reduce the burden of subsequent separation and purification, which provided an important prerequisite for the development of a new process for the recovery of Mo and V from HDS spent catalysts in alkaline systems.

(Invited) Nanowire Catalysts and Adsorbents

The unique properties of nanowire materials like fast charge transport, short diffusion length, controlled surface sites and single crystal nature make them ideal for designing high performance catalysts, adsorbents and electrocatalysts by design. To realize any of these applications, one would need either large quantities of nanowire powders or nanowire arrays on large areas. In this presentation, we will highlight our group’s efforts with scalable methods for continuous manufacturing of nanowire powders and arrays for oxides1 and III-nitride materials.2 The process for producing metal oxide nanowires has been scaled up to ton-scale. The resulting nanowire powders can be used to formulate unique catalyst and adsorbent products.Zinc oxide nanowires alloyed with catalytically active metals and have been formulated into ultra-deep desulfurization catalytic adsorbents.3,4 These materials exhibited ultra-deep desulfurization with sulfur removal down to 1 ppm or below for liquid hydrocarbons (diesel, gasoline and naphthalene) and to less than 1 ppb for natural gas. The desulfurization mechanism does not involve formation of H2S species unlike that typically observed with hydro-desulfurization process involving sulfided catalysts.Titania nanowires supported with nickel and molybdenum clusters have also shown to exhibit high activity and durability as hydro-desulfurization catalysts for removal of sulfur from hydrocarbons by forming H2S.5 The synergistic activity with MoS2 and titania are expected to contribute to enhanced activity with desulfurization.Alloying of nanowires with other elements is also studied to produce compound and alloyed nanowires. Fundamental studies have shown that alloying process occurs at much lower temperatures than decomposition temperatures for precursors used. Alloying studies have clearly shown that the solubility in nanowires to be much more than that expected for bulk materials systems. This presentation will provide several examples in which nanowires were alloyed with elements at compositions more than that expected for thermodynamic solubility.In the case of CO2 sorbents, alkali metal oxide nanowires have shown high capacity for CO2 sorption as high as 75% by wt. The alkali metal oxide nanowires have been alloyed with alkali hydroxides to produce alkali metal oxide compound nanowires. These solid sorbents showed selective CO2 sorption from a variety of streams including air, exhausts containing CO2 at various concentrations. Nanowire geometry for these nanowires allow for non-sinterability, and smaller length scales for rapid diffusion of alkali ions allow for fast kinetics and regenerability. 6,7 Acknowledgements: Authors also acknowledge contributions from Drs. Juan He, Sivakumar Vasireddy, Vivekanand Kumar, Veerendra Atla and Tu Nguyen. Partial support from National Science Foundation (NSF) and US Department of Energy (DOE) EPSCOR programs and full support from NSF and DOE SBIR programs and Kentucky Cabinet for Economic Development for Advanced Energy Materials, LLC are highly appreciated.

Sulfured FeMo carbides and nitrides catalysts upgrade extra heavy crude oil quality

In the context of the energy transition scenario, effective sulfur management is crucial. Enhancing the quality of extra heavy crude oil (EHCO) through catalytic processes, specifically hydrotreatment, is essential for reducing pollutant emissions like SOx into the atmosphere. Traditional hydrotreatment, utilizing MoS2-based catalysts typically on Al2O3 support, faces challenges with EHCO due to its elevated S and N content, which hampers catalyst efficiency. Metal carbides and nitrides exhibit promising electronic structures that confer resistance to deactivation in the presence of heteroatoms. This study compares the catalytic performances of Fe-promoted Mo sulfides, carbides, and nitrides (FeMoS(C,N)) in the thiophene hydrodesulfurization (HDS) reaction, serving as a model molecule for sulfur removal. Subsequently, we investigate the upgrading of a Venezuelan EHCO in terms of pollutant reduction, API gravity, and feedstock aromaticity. Catalysts were prepared from oxide precursors, varying the (Fe/(Fe+Mo)) atomic ratios (x = 0.00, 0.10, 0.33, 0.50, and 1.00), employing a temperature-programmed reaction protocol. Catalytic upgrading of EHCO was conducted in a stirred batch reactor, and the results were compared with a commercial CoMo-based catalyst. FeMoC(N) outperformed the commercial catalyst in sulfur removal. The elemental composition and nitrogen content of the feed remained constant; however, the sulfur content of asphaltenes decreased. Furthermore, the API gravity of crude oil increased when employing FeMoS and FeMoN catalysts, except with FeMoC, possibly linked to dealkylation reactions and the enrichment of lighter fractions with alkanes. FeMoN increased asphaltene aromaticity, while FeMoC decreased it. These results highlight the promise of FeMoC(N) as catalysts for HDS and upgrading heavy feedstocks.

Fabrication of an innovative phosphonate Schiff base adsorbent for molybdenum adsorption and its applications for molybdenum adsorption from spent hydrodesulfurization catalyst

AbstractBACKGROUNDTo investigate the recovery of molybdate from water and hydrodesulfurization catalysts, a novel synthesized phosphonate Schiff base, 4,4′‐(((2,2‐dimethylpropane‐1,3‐diyl) bis(azaneylylidene)) bis(methaneylylidene)) bis(2‐methoxyphenol) (HMI) and 4‐(((3‐((4‐(((S)‐hydroxyhydrophosphoryl)oxy)‐3‐methoxybenzylidene) amino)‐2,2‐dimethylpropyl)imino)methyl)‐2‐methoxyphenyl hydrogen phosphonate (HIMP), was utilized. This study aimed to assess the structural and property aspects of this synthesized compound using diverse characterizations, including FTIR, Thermogravimetric Analysis (TGA), mass spectrometry (GC–MS), fluorescence transfer spectra, scanning electron microscopy (SEM), and 1H‐NMR, 13C‐NMR, and 31P‐NMR.RESULTSThe study systematically examined several factors controlling molybdate recovery, including temperature, adsorbent dosage, pH, interaction time, and molybdate concentration using the batch technique. Optimal sorption effectiveness was achieved at pH 2, with an interaction time of 40 min, a 0.06 g adsorbent dose, at ambient temperature. The newly devised adsorbent exhibited an impressive adsorption capacity (Qe) of 372.54 mg of Mo per gram, with empirical data fitting the Langmuir and D‐R adsorption models. The kinetics of molybdate uptake followed second‐order kinetics. Thermodynamic aspects, including ΔG°, ΔS°, and ΔH°, were also investigated, providing appreciated perceptions into the energetic dynamics of the sorption process. Additionally, molybdate adsorption in the occurrence of other ions was explored, highlighting the selectivity of the modified phosphonate Schiff base for molybdate removal.CONCLUSIONThe study underscores the potential of the modified phosphonate Schiff base as a crucial adsorbent for molybdate elimination from both solutions and spent hydrodesulfurization catalysts. The findings offer important insights into the adsorption kinetics, thermodynamics, and selectivity of the adsorbent, enhancing our understanding of molybdate recovery processes and their broader applications. © 2024 Society of Chemical Industry (SCI).

Efficient recovery of all valuable metals from spent HDS catalysts: Based on roasting mechanisms for enhanced selective leaching and separation

Recovery of all valuable metals such as Ni, Mo, V and Al from spent hydrodesulfurization (HDS) catalysts is beneficial to environmental protection and resource recycling. The current recycling process mostly considers the recovery of Mo and V than recovery of Ni and Al, and generates a large amount of difficult-to-decompose Ni-Al residue and wastewater. Aiming at the insufficiency of the current recycling process, in this study, a novel pyro-hydrometallurgical process for efficient and complete recovery of metals from spent HDS catalysts was proposed. The mechanisms of phase transformation during roasting and leaching are investigated by XRD, XPS and SEM in depth. The modulation of the phase transformation of the spent HDS catalyst in the oxidative roasting process is the key to the influence on the leaching of Ni and Al. Inhibition of θ-Al2O3 phase and Ni-Al spinel generation by controlled roasting can achieve efficient leaching of Mo, V, Ni and Al. Subsequently, Mo and V were selectively leached with 2 mol/L Na2CO3, and the alkaline leach residue obtained was treated with 6 mol/L HCl. The results showed that alkaline leaching efficiencies of Mo and V reached 99.73 % and 91.86 % while acid leaching efficiencies of Ni and Al reached 99.71 % and 90.27 %, respectively. The metals of acid leach solution were recovered by using N235, HBL110 and NaAlO2 stepwise. This new process has the advantages of high efficiency and comprehensive metal recovery, high product purity, and low amount of slag and wastewater, and has good prospects for industrial application.

Novel titanium silicon micro-mesoporous composites via nano-assembly strategy for efficient hydrodesulfurization of dibenzothiophene

A unique hierarchical TS-1/FDU-12 (TF) micro-mesoporous composite was synthesized by nano-assembly method, and was used as an excellent support for high-efficiency hydrodesulfurization (HDS) catalyst (NiMo/TF) of dibenzothiophene (DBT). The introduction of TS-1 nanocrystals provided more S vacancies and more acidic sites to the NiMo/TF catalysts, and showed no effect on the highly ordered three-dimensional structure of the composites, leading to excellent HDS performance of NiMo/TF catalysts. The superior acidity of NiMo/TF favored the HYD pathway of DBT, resulting in improved DBT HDS activity with up to 98.0 % desulfurization degree. In addition, NiMo/TF presented an optimal reaction rate constant (kHDS) of 5.9 × 10-4 mol g-1 h−1, a turnover frequency (TOF) value of 1.6 h−1 and a low activation energy (Ea) of 47.7 kJ mol−1, which are due to the synergistic effect of large specific surface area, appropriate pore size, abundant Brønsted & Lewis acidic sites, suitable MSI, high sulfurization degree and highly dispersed MoS2 active phases.